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#41 Interceptor121

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Posted 29 March 2014 - 12:57 PM

I believe he may be working on a way to adjust it without removing the screws but this will do meanwhile. My led face front and outward so really not easy to see

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#42 diverdoug1

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Posted 29 March 2014 - 01:33 PM

The Backscatter video on their vacuum system details their non-led unit, not their electronic unit.  The electronic unit is about $100 USD more.  I like it because I know that the vacuum is still in effect without having to plug in the gauge. I also have a Nuaticam system with a vacuum system that I like a lot.  They both preload the o-rings, which greatly decreases the risk of flooding at the surface.


Edited by diverdoug1, 29 March 2014 - 01:43 PM.


#43 Interceptor121

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Posted 29 March 2014 - 02:29 PM

I think the backscatter video is pretty accurate. 200mbar or 5inhg keeps the ports on. 400mbar or 10inhg keeps it locked however if you don't have the gauge you don't actually know how much vacuum you have. Without having to go over and over the subject again the nauticam mirrorless and compact housing rotary latch do crack open if you hit on the red release button and you have the ordinary 200 mbar. When i mentioned to miso about pumping more vacuum to resist any temperature changes and false alarms he was not that keen as the system is set for 200mbar difference and more vacuum can delay a real alarm to be triggered. If I was concerned to get a hard vacuum in the housing i would get a gauge to take it to 400mbaf and forget about the in water alarm entirely and rely on a moisture sensor as in water flood alarm
Again a matter of personal preferences and not absolute rules

Edited by Interceptor121, 29 March 2014 - 02:30 PM.

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#44 Stuart Keasley

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Posted 29 March 2014 - 02:32 PM

I have the leak sentinel and I don't know where I said anything about hugyfot??
Personally I can't see the led of the leak sentinel I know miso is working on an improvement to adjust the position of the led as this may less visible depending on the position of the valve

Apologies, read Hugyfot as Backscatter (but I think you knew that)
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#45 Interceptor121

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Posted 29 March 2014 - 02:41 PM

Apologies, read Hugyfot as Backscatter (but I think you knew that)


No but I don't need to actually tests that specific system to see what it does. The difference with the others is that you have a gauge so if you wanted to make your own decision and pump more vacuum you can do it reliably otherwise you need to make assumptions i.e double the stroke from the moment the led is green
Ideally you would like to be able to change the trigger point of the led to suit your preferences for example if you wanted to literally lock it

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#46 diverdoug1

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Posted 29 March 2014 - 06:19 PM

       Any amount of negative pressure in the housing will help prevent dislodgement of a housing or port o-ring at the surface.  Even 1 inch of Hg will help preload the O-rings.  A simple Google search of the keywords "o-ring" and "preload" will help illustrate this.  I guess the pushback we are seeing is a result of the statement that a vacuum "makes no difference" in the risk of flooding at the surface, which is incorrect.  Most of this thread has been carried by repeated misguided, transparent, overly complex attempts to support that initial incorrect statement.  I have found that most people will respect those who are big enough to admit when they are wrong, and will ridicule those who are not.

        Wetpixel is a wonderful resource for learning and sharing knowledge about underwater photography.  The only way we can trust the information that we gain from this website is for us to call out the posting of erroneous information.  I hope that if someone were to post misinformation about a subject that I am trying to learn about, my fellow photographers in the Wetpixel community would call it out.  I also hope that if I inadvertently post erroneous information, you will all set me straight.


Edited by diverdoug1, 29 March 2014 - 10:59 PM.


#47 Interceptor121

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Posted 29 March 2014 - 11:15 PM

Why are you getting so hung up? Oring systems are not all the same. What you say may be true for a system where the oring sits right between the closure but not true for another where it sits on a grove and sideways compared to the housing closing direction. You want to go ahead and give advice based on your housing that's fine but the op housing is not the same the oring don't sit like yours and if you press the lock button it cracks open. The initial question was I have an housing for the em5 and I want to put a vacuum system can I now be less careful with rough water entries? Based on the housing the op has (nauticam em5) i would say no because that specific housing can be opened if you accidentally hit the lock button and rotate the latch. I have an housing with the same lock mechanism and it does exactly that. I discovered it myself when I first installed the leak sentinel and went ahead and opened it with one finger after having it pressurised and then realised the instructions said about releasing the valve. I didn't need to do that to open it and it doesn't even need to put strength to open. Probably this is due to the housing design and the way the oring sit. If you want to make some blanket statement based on the housing you have feel free ring ahead but in my opinion that is not the case and varies housing by housing and for the specific one the op has your rule does not apply. Now you should cool down and read carefully what I have wrote before because contrary to you I have only addresses the op question

Edited by Interceptor121, 29 March 2014 - 11:15 PM.

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#48 diverdoug1

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Posted 29 March 2014 - 11:25 PM

I have a Nauticam EM5 housing, and am fully aware that it utilizes a cylinder seal type o-ring system

see http://www.fluorgum.com/static_seal_dynamic_seal.php

This type of seal relies on radial o-ring preload deformation. You may need to cut and paste the link to your browser for it to work.  The port and housing seals are more secure with even small increases in the pre-load.

Read and LEARN!

I think my preceding post answers your question as to why I am "so hung up".  I am calling out misinformation when I see it posted.  An information deficit only becomes a problem when you refuse to acknowledge it.


Edited by diverdoug1, 29 March 2014 - 11:52 PM.


#49 Interceptor121

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Posted 29 March 2014 - 11:30 PM

Have you tried pushing a finger on the red button once the green light is on? Try it you may be surprised. I will post a video later of my housing opening

Ps link not working

Edited by Interceptor121, 29 March 2014 - 11:31 PM.

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#50 diverdoug1

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Posted 29 March 2014 - 11:44 PM

I told you that you must cut and paste the link to your browser.

Also, pushing the red button will pop the seal, but the seal at the surface is more secure with a vacuum preload.  You are also neglecting the increased security of the port o-ring.


Edited by diverdoug1, 29 March 2014 - 11:45 PM.


#51 Interceptor121

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Posted 29 March 2014 - 11:52 PM

So it did open as I said.
Am not neglecting anything. The 200bar will hold a port in place but that's not the point. The question was can I make more rough entries? Answer is you should not. That the vacuum will keep a loose item to fall is also true nobody is denying. And on a classic housing like the big SLR and video where the oring are squeezed 400mbar will definitely be very hard to open. So it seems we are in agreement and maybe you should be more careful with certain statements or accusations. Am just trying to make the op aware that having a vacuum system in his specific circumstances is not a blanket insurance policy and definitely not as effective as an airlock system than other shapes of housing

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#52 Stuart Keasley

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Posted 29 March 2014 - 11:59 PM

Why are you getting so hung up? Oring systems are not all the same. What you say may be true for a system where the oring sits right between the closure but not true for another where it sits on a grove and sideways compared to the housing closing direction. You want to go ahead and give advice based on your housing that's fine but the op housing is not the same the oring don't sit like yours and if you press the lock button it cracks open. The initial question was I have an housing for the em5 and I want to put a vacuum system can I now be less careful with rough water entries?

People are getting bothered because you have given out duff information, contrary to every other persons input and the various sources.

There are two types of o-ring installation, facing and barrel, they've got slightly different pros and cons, but beyond that they all work in exactly the same way (regardless of whether they're installed in a camera housing, engine block or an aircraft). The mechanics of o-rings are nicely described in the Parker's document I linked to at the start if this thread (the document is not specific to aircraft)


The initial question was

I know vacuum systems like that are designed to verify seal integrity and alert the user to a problem pre-dive and during the dive.  Beyond that, do these systems provide any meaningful protection against flooding?  I am wondering if placing the housing under that kind of "negative" pressure pre-dive makes it less likely to flood at the surface such as in a rough shore entry or having to giant stride off a boat.

That's quite different to your translated question above.

A full answer to that question is:

Yes, it will make it less likely to flood, as any negative pressure in the housing will help further preload the o-rings and create a better seal when compared to a housing that has only mechanical (e.g latch) pressure applied to the o-ring.

However rough shore entries, giant stride entries etc could still result in a flood. The pressure tester is best considered as an additional check on good practice and housing integrity, as opposed to a replacement for the normal care you would take with a camera and housing.

Edited by Stuart Keasley, 30 March 2014 - 12:03 AM.

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#53 diverdoug1

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Posted 30 March 2014 - 12:01 AM

No interceptor, you said it would "make no difference", which is incorrect!  No system is a "blanket insurance policy".  Had you stated that, no one would have argued with you, but that is NOT what you said.  If you are modifying your opinion, fine.  Regardless of your opinion, even if a port does not become dislodged, water intrusion can occur by blow-by in a low preload state.  That is why aggressive drying with high pressure air can lead to water intrusion after a dive.


Edited by diverdoug1, 30 March 2014 - 12:07 AM.


#54 Interceptor121

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Posted 30 March 2014 - 12:03 AM

Which is the same thing I said really? And the housing in question does open if you hit the button despite predicaments it would not. So i would be careful about making statements about duff information as the one about that specific housing staying closed was in fact incorrect.

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#55 Stuart Keasley

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Posted 30 March 2014 - 12:10 AM

Which is the same thing I said really?

No it is not!

You stated categorically that it makes no difference, and then went on to argue that pressure preloading is not relevant.

That is wrong, that is what people are pulling you up on.
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#56 diverdoug1

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Posted 30 March 2014 - 12:15 AM

The op did not ask if he could hit the release button, and no one said he could.  The button has nothing to do with it.  O-ring seating can be dislodged even with the mating surfaces in place without adequate preload.  Hitting the release button uncouples the mating surfaces.  

Allow me to make an analogy to clarify this for you.  You are standing in your garden wearing your scuba mask.  The mask strap is adjusted lightly on your face so that it produces a watertight seal when you gently dip your head in the water.  If you shoot your garden hose nozzle at the area where the mask meets your face, water will shoot in, but if you suck in through your nose, the increased negative pressure may prevent the leak.  If you cut your mask strap (hit your red button) the mask will fly off.

Admittedly, this analogy does not address the way that an active seal o-ring preloads, but may help you with an intuitive feeling for what we are trying to explain to you.


Edited by diverdoug1, 30 March 2014 - 12:31 AM.


#57 Interceptor121

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Posted 30 March 2014 - 12:23 AM

Hitting the button could happen in a rough shore entry or not? A 200 mbar vacuum system is a leak detection system not an anti flood system though it may have the added benefit of keeping together some poorly assembled parts. A higher vacuum system 400+mbar is more likely to be called a leak prevention system. However unless you buy the backscatter pump or your own gauge you can't determine following the user instructions at hand what vacuum you have created in excess of 200mbar so you are not using a leak prevention system just a leak detection system. I guess manufactures are aware of that and that is why those are leak detection systems and not leak prevention systems? Enough now I leave to you experts

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#58 Interceptor121

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Posted 30 March 2014 - 01:03 AM

The op did not ask if he could hit the release button, and no one said he could.  The button has nothing to do with it.  O-ring seating can be dislodged even with the mating surfaces in place without adequate preload.  Hitting the release button uncouples the mating surfaces.  
Allow me to make an analogy to clarify this for you.  You are standing in your garden wearing your scuba mask.  The mask strap is adjusted lightly on your face so that it produces a watertight seal when you gently dip your head in the water.  If you shoot your garden hose nozzle at the area where the mask meets your face, water will shoot in, but if you suck in through your nose, the increased negative pressure may prevent the leak.  If you cut your mask strap (hit your red button) the mask will fly off.
Admittedly, this analogy does not address the way that an active seal o-ring preloads, but may help you with an intuitive feeling for what we are trying to explain to you.

Hahahaha
Let me make another example to help you. If you breathe slightly in (ie leak system with 200 mbar pressure) that mask will quite easily fly off with a splash from the side or if you run around too much (rough water entry) but if you have to suck so hard to pop your eyes out (400 mbar vacuum) you can most likely run around and it will stay in place. So the amount of abuse you can sustain depends on the vacuum applied if you don't have a way to measure thy you don't know if you can walk or run so better walk. Now it's really enough for you gang and must be early in us at this time

Edited by Interceptor121, 30 March 2014 - 01:12 AM.

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#59 Stuart Keasley

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Posted 30 March 2014 - 01:11 AM

Hitting the button could happen in a rough shore entry or not? A 200 mbar vacuum system is a leak detection system not an anti flood system though it may have the added benefit of keeping together some poorly assembled parts. A higher vacuum system 400+mbar is more likely to be called a leak prevention system. However unless you buy the backscatter pump or your own gauge you can't determine following the user instructions at hand what vacuum you have created in excess of 200mbar so you are not using a leak prevention system just a leak detection system. I guess manufactures are aware of that and that is why those are leak detection systems and not leak prevention systems? Enough now I leave to you experts


Sorry, but that is nothing more than further self prescribed waffle.
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#60 Interceptor121

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Posted 30 March 2014 - 01:14 AM

Sorry, but that is nothing more than further self prescribed waffle.

Can you try to say something without having a go and be rude or is that difficult for you?

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